Effect of dietary supplementation with protease on growth performance, nutrient digestibility, intestinal morphology, digestive enzymes and gene expression of weaned piglets

摘要

Abstract This study was conducted to investigate the effect of dietary protease supplementation on the growth performance, nutrient digestibility, intestinal morphology, digestive enzymes and gene expression in weaned piglets. A total of 300 weaned piglets (21?days of age Duroc?×?Large White?×?Landrace; initial BW?=?6.27?±?0.45?kg) were randomly divided into 5 groups. The 5 diets were: 1) positive control diet (PC), 2) negative control diet (NC), and 3) protease supplementations, which were 100, 200, and 300?mg per kg NC diet. Results indicated that final BW, ADG, ADFI, crude protein digestibility, enzyme activities of stomach pepsin, pancreatic amylase and trypsin, plasma total protein, and intestinal villus height were higher for the PC diet and the supplementations of 200 and 300?mg protease per kg NC diet than for the NC diet ( P Keywords Growth performance ; Nutrient digestibility ; Morphology ; Gene expression ; Weaned piglets prs.rt("abs_end"); 1. Introduction The cost of pork production mainly comes from the feed, and the significant increases of feed cost during the last decade have reduced profit margins of pork production ( Schmit et?al., 2009 ). The use of exogenous feed enzymes has been one of the most widely used strategies to improve nutrient utilization efficacy and reduce the feed cost in the animal industry ( Adeola and Cowieson, 2011 ). Proteases have been routinely included to swine diets for many years as part of enzyme cocktails containing xylanases, celluase, amlyase and glucanases ( Yin et?al., 2001 , Yin et?al., 2004 , Omogbenigun et?al., 2004 , Ji et?al., 2008 and Jo et al., 2012 ). An enzyme cocktail (β-glucanase, xylanase and protease) improved the digestibilities of crude protein and energy at ileal and the total tract levels of the hulless barley based diets for young piglets ( Yin et?al., 2001 ). Similarly, an enzyme cocktail (arabinoxylanase and protease) improved the nutritional value of diets containing wheat bran or rice bran for growing pig ( Yin et?al., 2004 ). Dietary supplementation with enzyme cocktails including proteases improved nutrient utilization?and growth performance in weaned pigs ( Omogbenigun et?al., 2004 ). A beta-glucanase-protease enzyme blend product improved the ileal digestibility of crude protein and other nutrients ( Ji et?al., 2008 ). Supplementation of 0.05% of enzyme cocktails (α-amylase, β-mannanase, and protease) to a corn and soybean meal (SBM) diet or a complex diet?improved the performance of growing pigs ( Jo?et?al., 2012 ). Although the above positive effects have been reported, the contribution of protease on these improvements is still not clear. Recently, proteases have been used alone in the pig diets with the availability of several commercial stand-alone proteases, and new mechanisms of action have been proposed ( O'Doherty and Forde, 1999 , McAlpine et?al., 2012a , McAlpine et?al., 2012b and Guggenbuhl et?al., 2012 ). However, efficacy of protease in weaned piglets and its mechanisms behind are still not clear especially when low digestible protein sources are used. Therefore, this study was conducted to investigate the effect of dietary supplementation with protease on the growth performance, nutrient digestibility, intestinal morphology, digestive enzymes and gene expression in weaned piglets. 2. Materials, methods and management 2.1. Animals and diets A total of 300 weaned piglets (21?days of age Duroc?×?Large White?×?Landrace; initial BW?=?6.27?±?0.45?kg) were provided by Wens Group (Guangzhou, Guangdong). They were randomly divided into 5 groups (60 piglets per group and 10 piglets per pen). All piglets were housed in environmentally controlled rooms equipped with water nipples and stainless-steel feeders. Diets and water were offered ad libitum throughout the duration of the experiment. Room temperature and air humidity were maintained at 25°C and 50%, respectively. All procedures were approved by the Animal Care Committee at the South China Agricultural University. The animals used in this experiment were cared for in accordance with the guidelines established by University Council of Animal Care. As shown in Table?1 , the basal diets used were formulated to meet the nutrient requirement of pigs ( NRC, 2012 ). For 14?d, piglets were fed the following diets: 1) a standard commercial diet, named as a positive control (PC) diet (22.21% soybean meal, 5% whey protein?and 3% fish meal), 2) a negative control (NC) diet (30.06% soybean protein without whey protein and fish meal), 3) 100?mg protease per kg NC diet, 4) 200?mg protease per kg NC diet, and 5) 300?mg protease per kg NC diet. The protease used is a commercial protease (Jefo, Saint-Hyacinthe, Canada). The five diets were iso-nitrogenous and iso-caloric, and pelleted at a condition of 0.4?MPa and 75°C. The major source of protein in the PC diet was from fishmeal and concentrated whey protein, which were substituted with soybean meal in the NC diet.